A new ion source, using negative primary ions, for liquid secondary ion mass spectrometry (LSIMS) was designed and constructed. The most significant advantages were that 10 kV power supplies (compared to 20 kV for positive sources) were adequate, resulting in simpler design requirements and reduced electrical arcing in the source. A highly focused point source was fitted to a double focusing mass spectrometer which was also equipped with a moveable target. An ion optical system was designed and constructed so that secondary ions formed on a flat surface could be extracted and injected into the mass spectrometer. Intense secondary ion currents (about 10 to the -11 amps) were obtained frm organic compounds, despite the power dissipation of about 10,000 watts/square cm2. By use of a piezoelectric-effect crystal motor system and microcomputer, it was possible to move the sample reproducibly in 10 to the -8 m steps (10 nm) in two directions. Surface distributions of organic chemicals could be obtained with a spatial resolution less than 1 micron. The idea of chloride attachment negative chemical ionization (NCI) mass spectrometry was extended to HPLC/MS. The world's first tandem high resolution mass spectrometer was built to our specifications and installed. This instrument permits simultaneous high mass resolution on both parent and daughter ions. Of perhaps greater environmental health interest, moderate resolutions can be achieved on both parents and daughters at good sensitivity. Initial studies have demonstrated the power of this instrument for the characterization of peptides, corticosterones and phospholipids from biological sources. Advantages include greatly increased analytical information and a much reduced susceptibility to sample contamination. In addition to the new tandem instrument, the use of kinetic energy release (KER) measurements has been extended from its traditional role in the study of gaseous ion chemistry to the characterization of unknown organic compounds. A new time-of-flight design has been developed which offers resolution equal to or better than that achieved when magnetic instruments are operated at very high mass (i.e., greater than 8000 daltons).